Fluid handling by foam wound dressings: From engineering theory to advanced laboratory performance evaluations

This article describes the contemporary bioengineering theory and practice of evaluating the fluid handling performance of foam-based dressings, with focus on the important and clinically relevant engineering structure-function relationships and on advanced laboratory testing methods for pre-clinical quantitative assessments of this common type of wound dressings. The effects of key wound dressing material-related and treatment-related physical factors on the absorbency and overall fluid handling of foam-based dressings are thoroughly and quantitively analysed. Discussions include exudate viscosity and temperature, action of mechanical forces and the dressing microstructure and associated interactions. Based on this comprehensive review, we propose a newly developed testing method, experimental metrics and clinical benchmarks that are clinically relevant and can set the standard for robust fluid handling performance evaluations. The purpose of this evaluative framework is to translate the physical characteristics and performance determinants of a foam dressing into achievable best clinical outcomes. These guiding principles are key to distinguishing desirable properties of a dressing that contribute to optimal performance in clinical settings. The current research was conducted by members ofthe International Wound Dressing Technology ExpertPanel (iWDTEP). The iWDTEP consists of consultantspaid by Mölnlycke Health Care AB (Gothenburg,Sweden). Mölnlycke has not controlled (or regulated)the research carried out by the members of the iWD-TEP. The authors would like to acknowledgeMs. Victoria Teng of the Physical Testing Laboratory at Mölnlycke Health Care for the performance ofexperiments using the FLUHTE wound simulatorsystem

Nitrogen translocation between Alnus glutinosa (L.) Gaertn. seedlings inoculated with Frankia sp and Pinus contorta Doug ex Loud seedlings connected by a common ectomycorrhizal mycelium

Uptake and translocation of nitrogen was studied in laboratory microcosms consisting of Alnus glutinosa (L.) Gaertn., Frankia sp., Paxillus involutus (Fr.) Fr. and Pinus contorta Dougl. ex Loud. P. involutus was shown to form a fully functional ectomycorrhizal association with alder as well as pine, and the seedlings thus became interconnected by a common mycelium. When microcosms were exposed to N-15(2) gas, interplant translocation of N-15 was observed in two out of three experiments. N-15(2) was fixed by Frankia and translocated to all other parts of the system. In the two experiments in which interplant translocation occurred, between 5 and 15 % of the N-15 recovered was found in the pine seedlings. Within seven days, fixed N2 was incorporated into amino acids in the Frankia nodules, translocated to both the A. glutinosa and P. contorta seedlings and incorporated into macromolecules. In alder seedlings, citrulline and ornithine were the free amino acids that had both the highest N-15 enrichment levels and concentrations. In pine, glutamine and citrulline had the highest N-15 concentrations, and glutamine had the highest level of N-15 enrichment. N-15 enrichment levels were greatest in the nodules, at between 5.5 and 29 % in the different amino acids and 12 % in the macromolecular fraction. Enrichment levels decreased with increasing distance from the nodules. The uptake and translocation of N-15 applied as (NH4Cl)-N-15 to the mycelium was also studied. N-15 was incorporated into amino acids in the mycelium and translocated further in this form. Generally, free amino acids had high N-15 enrichment levels in the mycelium, decreasing along the translocation pathway. Citrulline and glutamine were the amino acids with highest N-15 concentrations in all parts of the system. N-15 was also found in the macromolecular fraction

The influence of substrate pH on carbon translocation in ectomycorrhizal and nonmycorrhizal pine-seedlings

The effects of changed substrate pH on translocation and partitioning of C-14-labelled plant assimilates were examined in laboratory microcosms containing mycorrhizal (unidentified fungal isolate 'Pink FMT 87:2') and non-mycorrhizal seedlings of Pinus sylvestris L. and Pinus contorta Dougl. ex Loud. The mycorrhizal plants had intact mycelial systems at different developmental stages, and microcosms contained non-sterile peat (pH 3.8) or peat adjusted to different pH values with CaO. In systems with mycorrhizal mycelium which had just started to colonize the peat no significant differences in C-14 assimilation were found, either with respect to substrate pH or mycorrhizal status of the plant. Loss of activity from the mycorrhizal plants was more rapid, however, probably mainly as a result of increased respiration from the infected root systems. After 8 wk growth in peat at pH 3.8 and 5.2 shoot weights of all seedlings were the same, whereas non-mycorrhizal plants had root systems twice the size of the mycorrhizal ones. In plants with well developed extramatrical mycelia translocation of labelled carbon to the mycelium growing at pH 3.8 was faster than that to mycelium growing at pH 5.2. After 4 d incubation, however, the percentage of the originally supplied carbon present in the mycelium was 5 % regardless of substrate pH. Activity found in the peat surrounding non-mycorrhizal plants rarely exceeded 0.3 %

Arbuscular mycorrhizal fungi respond to the substrate pH of their extraradical mycelium by altered growth and root colonization

To test the response of arbuscular mycorrhizal (AM) fungi to a difference in soil pH, the extraradical mycelium of Scutellospora calospora or Glomus intraradices, in association with Plantago lanceolata, was exposed to two different pH treatments, while the root substrate pH was left unchanged. Seedlings of P. lanceolata, colonized by one or other of the fungal symbionts, and nonmycorrhizal controls, were grown in mesh bags placed in pots containing pH-buffered sand (pH around 5 or 6). The systems were harvested at approximately 2-wk intervals between 20 and 80 d. Both fungi formed more extraradical mycelium at the higher pH. Glomus intraradices formed almost no detectable extraradical mycelium at lower pH. The extraradical mycelium of S. calospora had higher acid phosphatase activity than that of G. intraradices. Total AM root colonization decreased for both fungi at the higher pH, and high pH also reduced arbuscule and vesicle formation in G. intraradices. In conclusion, soil pH influences AM root colonization as well as the growth and phosphatase activities of extraradical mycelium, although the two fungi responded differently

Identification of cytoskeletal components in pine ectomycorrhizas

Ectomycorrhizal associations were synthesized between pine seedlings and the fungi Suillus bovinus (L.) ex Fr. or Paxillus involutus (Batsch ex Fr.) Fr. Immunoblotting of polypeptides separated electrophoretically from crude tissue extracts revealed the abundant presence of tubulin and actin in ectomycorrhiza and lower amounts in the fungal strands surrounding the ectomycorrhizal roots. In ectomycorrhiza the alpha-tubulins from fungal hyphae and plant cells were clearly distinguishable but such discrimination was not possible for beta-tubulin or actin due to the similar mobility of proteins originating from the conifer and fungal tissues. Young ectomycorrhizal short roots were fixed while still attached to the seedlings and, using indirect immunofluorescence microscopy with tubulin antibodies, microtubules were detected in both the conifer cells and in fungal hyphae. In the host plant cytoplasmic and spindle microtubules were visualized in meristem cells and in differentiating vascular tissue but not in the cortical cells. In symbiotic hyphae the microtubule tracks and spindles of dividing nuclei were clearly distinguished in the mantle hyphae in the tip region of the short roots. In the Hartig net hyphae microtubule tracks changed to a less clear, reticulate structure. Actin was visualized as long filaments in vascular tissue cells and as small microfilament bundles in mantle hyphae. Short microtubules and actin dots were detected in cytoplasm-containing hyphae on the strand surface. The possible role of the cytoskeletal elements in the maintenance of the ectomycorrhizal association is discussed